The present invention relates to a wavelength-varying multi-wavelength light source applicable to non-linear effect induction such as a wavelength-division multiplexing optical communication or 4 optical wave mixing, and more particularly to a wavelength-varying multi-wavelength optical filter laser using a single pump light source capable of converting wavelength, which is further serviceable and uses few assemble parts as compared with the prior art.
In general, necessity of a wavelength-division or a frequency-division multiplexing for a wide band optical communication has been tending upwards more and more, now. A wavelength-varying multi-wavelength light source may play a very important role in embodying said multiplexing.
In a wavelength-division or a frequency-division multiplexing, an optical fiber laser or a semiconductor laser may be used as a light source which is capable of a wavelength conversion or oscillates at different wavelengths.
In order to obtain the desired wavelength, the prior semiconductor laser which is used as a light source oscillating at different wavelengths as above described, may be used by fabricating in one chip through a complicate process or by constituting a wavelength-varying semiconductor laser.
However, the wavelength-varying semiconductor laser causes the problems that the entire configuration is complicate as well as it is difficult to obtain a multi-wavelength output.
The above problems are to be explained in detail hereinafter with reference to accompanying drawings.
FIG. 1 shows a diagram illustrating the prior wavelength-varying multi-wavelength optical filter laser using a wavelength-varying optical filter. As shown in FIG. 1, the prior wavelength-varying multi-wavelength optical filter laser using a polarizer POL and a polarization controller PC laser has been proposed. However, the prior laser is difficult to extend multi-wavelengths because it has instability that the polarization is changeable due to a trifling distortion of an optical fiber and it has lower practical use due to a large bulk of the polarization controller.
FIG. 2 shows the prior wavelength-varying multi-wavelength optical fiber laser using a wavelength-division multiplexer.
When the wavelength-division multiplexers is originally fabricated, mainly it is divided into the fixed wavelength, so that the optical fiber laser has no a wavelength-varying characteristic.
The prior laser that makes a ring-type optical fiber laser cavity using a single mode optical fiber containing rare earth elements for gain and a multi-mode optical fiber and obtains a multi-wavelength laser output using a filter characteristic depending on a wavelength due to spatial mode beating between two basic mode LP.sub.01 and LP.sub.11 in the multi-mode optical fiber, has been proposed.
However, the prior laser has problems that the wavelength space of a multi-wavelength laser should be control in accordance to a length of a multi-mode optical fiber and it has no a separate wavelength-varying characteristic of each laser wavelengths.